Tempest in a Teapot: Michael Lewis’ Flash Boys Solves a Problem that is Barely There

Michael Lewis is the finest writer in a generation to turn his attention to the practice of finance, but in Flash Boys: A Wall Street Revolt – his account of high-frequency trading (HFT) and of a likeable trader who found a way to beat it – he is a few steps off base. Flash Boys is a terrific read, with dashing heroes and dastardly villains. But life isn’t like that, and HFT is neither good nor evil. It’s a new way of profiting from the trading activity of buyers and sellers of equities. It either raises or lowers total transaction costs by a small amount, but we have no way of knowing which.

Lewis is convinced that HFT is evil and needs to be stopped. In contrast, I believe in evaluating business practices using data about their costs, benefits and unintended consequences and letting those practices be unless they are clearly dishonest and harmful. Applying those criteria to HFT, I am not convinced of its harm. Of course, it is entirely proper that we should look for ways to trade against HFT and keep some of the profit for our clients and for ourselves. That is exactly what Brad Katsuyama, Lewis’ hero, did, and he should be commended for his work.

Flash Boys did teach me a lot about modern market institutions, which are so new and complex that most people don’t understand them at all. Investment professionals need this knowledge – they should not imagine that the stocks they analyze and trade are brokered in the way that they were in the last century.

But Lewis’ animus against HFT, while understandable, should not be the basis for setting policy.

Brad Katsuyama’s discovery

Flash Boys has been so widely read and discussed at this point that only a brief summary is needed. In the middle of the last decade, Brad Katsuyama, a young Canadian trader, discovered that the stock purchase and sale orders that he placed on various stock exchanges on behalf of his customers had suddenly become more difficult to execute. As soon as he began to trade, the price would change in a manner unfavorable to his brokerage customers. Every time.

This had not happened before. As Katsuyama eventually discovered, HFT firms were front-running his trades. “I’m the event…I am the news,” he explained to a trader wondering what news the market was reacting to.1 Other traders were trading on the news that Katsuyama was buying or selling.

Incredibly, the HFT firms had spent vast sums of money running fiber optics on straight lines between themselves and the exchanges. This enabled them to profit from the saving of a few precious milliseconds of communication time, making front-running possible.

Katsuyama first designed a system, called Thor, for his employer, Royal Bank of Canada (RBC), to deliver orders to the exchanges in a staggered way that prevented HFTs from front-running or otherwise profiting from the fact that he was trading. Then with several partners, he set up a new stock exchange, called IEX, that did the same thing. Their pitch to investors was that they would be treated fairly instead of being systematically ripped off. The exchange succeeded, on some days achieving more trading volume than the venerable NYSE MKT LLC, formerly called the American Stock Exchange.

Understanding HFT

HFT firms earn their living by capturing a part of the already-tiny spread between the bid and offer prices of stocks traded on an exchange. They do so in a way that is invisible to most investors. How can we begin to understand their activity and their impact?

The technical aspects of HFT are best left to Lewis, who has a special gift for making complicated concepts simple. Here, I’ll try to explain the economic impact of HFT, as I understand it.

HFT as a middleman

It’s possible to imagine a kind of HFT that is completely harmless and in fact beneficial. Let’s say that the “market” for 10,000 shares of a stock is $50.00 bid, $50.10 offer. (That is, someone stands ready to buy that number of shares if a seller willing to take $50 appears in the market, and someone stands ready to sell the same number of shares if a buyer willing to pay $50.10 appears.) Thus, in my example, 10 cents is the market maker’s hypothetical maximum gross profit (before subtracting the costs of doing business).

Now let’s say that a trader with an especially low cost of doing business would be satisfied with a 6-cent profit. He or she buys 10,000 shares at $50.02, sells them at $50.08 and makes a riskless profit of 10,000 × $0.06 = $600.

Because the investor who sought out originally to buy the stock has bought it from the trader for $50.08 instead of $50.10, the trader has provided “price improvement” of 2 cents per share, or $200 in total. The original seller sees the same amount of price improvement. Everyone wins except for the original market maker, who is knocked out of the game by this new, low-cost provider of what traders call liquidity.2 A HFT firm can, and sometimes does, create price improvement in the market in this way. If that were all that HFTs did, they would be relatively uncontroversial.

2. Usually, we think of liquidity as cash in the bank or a credit line. The kind of liquidity provided by a trader is slightly different – it’s the offer to convert securities to cash, or cash into securities, at a price very close to the last sale – but goes by the same name.